Efficiency in a centrifugal compressor with a vaneless diffuser housing can be affected by diffuser housing shape. Conventional housings use a pinch section followed by a parallel section that extends to the compressor scroll wherein the pinch section provides a throttle near the compressor wheel exit while the parallel section provides for diffusion. Various exemplary pinch and/or diffuser sections are disclosed herein that provide for increases in efficiency, for example, when compared to various conventional housings.
According to one aspect of the present invention there is provided a compressor wheel housing for a turbocharger compressor wheel the housing comprising: a substantially cylindrical shroud surface definable with respect to a radial dimension and an axial dimension along a rotational axis of a compressor wheel with an origin coincident with a z-plane of a compressor wheel wherein the axial position of the shroud surface decreases with increasing radial position to a compressor wheel blade outer edge radius; and a diffuser surface extending radially outward and axially downward from the cylindrical shroud surface, wherein the diffuser surface includes a minimum diffuser surface axial position at a radial position less than about 1.25 times the compressor wheel blade outer edge radius and wherein the diffuser surface includes a greater axial position at a radial position beyond that corresponding to the minimum axial position.
According to a second aspect of the present invention there is provided a compressor wheel housing for a turbocharger compressor wheel, the housing comprising: a substantially cylindrical shroud surface definable with respect to a radial dimension and an axial dimension along a rotational axis of a compressor wheel with an origin coincident with a z-plane a compressor wheel wherein the axial position of the shroud surface decreases with increasing radial position to a compressor wheel blade outer edge radius at an angle of about 20 degrees or less with respect to the z-plane; and a diffuser surface extending radially outward and axially downward from the cylindrical shroud surface wherein the diffuser surface includes a minimum diffuser surface axial position at a radial position less than about 1.25 times the compressor wheel blade outer edge radius and wherein diffuser surface approaches the minimum at an angle of about 10 degrees or less with respect to the z-plane.